Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Heads up Monday: Expect a stormy, dynamic, and ultimately dangerous day. New snow, rain, and warming temperatures should increase avalanche danger at all elevations. You could easily trigger storm, wind and loose wet avalanches. Avalanches could be large and surprising at upper elevations where buried wind slabs, and persistent weak layers may fail.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    New snow falling with warming temperatures should continue to pile up into the afternoon on Monday, especially in higher terrain near the crest. Warming temperatures are expected to create unstable and upside-down storm snow, and storm slabs could fracture easily off steeper features at all elevations. The snow will be stacking up over some colder, dry snow from Sunday and winds could create thicker slabs at higher elevations. East of Highway 97, expect wind slabs to be the main concern at upper elevations.

    Plan to stay off of steep slopes on Monday, especially if finding signs of instability like shooting cracks and small recent slides. Avalanches could be large at higher elevations where the new snow will be covering up older wind slabs, and a deeper layer of faceted grains over a crust. Above 5,500ft, NW-NE aspects harbor weaker, faceted grains over a crust from early March. This layer could be down 2ft deep or greater in some areas by Monday, and any avalanche that runs on it could be very large. 

    Example recent slab avalanche from the East South zone.

    Photo: Andrew Kiefer

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–1.5

    Rain on snow and warming temperatures is expected to set off a round of wet loose avalanches on Monday. Expect these to grow larger as the day warms up, and as the rain line creeps up the mountain sides. Signs of wet loose avalanche activity are rollerballs, and fresh fan-shaped avalanches with chunky looking debris.

    Be especially careful of going underneath larger steep slopes where slides could pack more of a punch and hit you from above. If you do go out, make a plan to avoid steep lower elevation slopes later in the day because rain on snow should make them unstable. 

    Example loose wet avalanches below treeline.

Avalanche Discussion

Expect a significant increase in avalanche danger from Sunday to Monday, as a warm front sends snow levels to 5,000ft during the daytime and creates dangerous conditions. Conditions should be dynamic, and what you find first thing in the morning may be much different a few hours later. Expect dangerous conditions with good chances for natural avalanches to run, especially at upper elevations and near the crest.

Observers have been documenting weaker, faceted grains and/or surface hoar overlying a crust from early March on NW-NE aspects from Stemilt Basin to Icicle Creek. Observers in the Chiwaukum range consistently found the weak layer above 5,000ft and reported significant wind loading on Saturday. I found the March 8th facets in the White Pine drainage above 5,500ft on Friday. A vague observation of large collapses in the Teanaway also came in from Saturday (unknown details). By Monday, there may be well over 2 ft of snow overlying these persistent weak layers at upper elevations on northern and eastern aspects. It appears likely that this storm could increase chances of triggering avalanches on this deeper layer, so Monday is a heads-up day.

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